Rewinder method and apparatus

ABSTRACT

A rewinder method and apparatus. The payout assembly of a rewinder machine comprises a spool having optical fiber wrapped about it, a motor that turns the spool as fiber is unwound from the spool, a first sheave having a surface along which the unwound fiber passes, a load cell in direct contact with the first sheave, and a motion mechanism for producing relative motion between the spool and the first sheave. The load cell senses stress exerted on the first sheave by the fiber as the fiber passes along a surface of the. The load cell produces electrical signals relating to the fleeting angle between the first sheave and the position on the spool from which fiber is being unwound. A controller receives the electrical signals and generates control signals that cause the motion mechanism to produce relative motion between the spool and the first sheave in a direction substantially parallel to an axis of rotation of the spool to reduce the fleeting angle.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention generally relates to proof testing optical fibers. More particularly, the present invention relates to a rewinder machine that is used to proof test optical fibers.

BACKGROUND OF THE INVENTION

[0002] A rewinder machine is a machine that proof tests optical fiber after the fiber has been manufactured and prior to shipment to a customer. A known rewinder machine is shown in FIG. 1. Generally, a rewinder machine comprises a payout assembly 1, a proof test assembly 2 and a takeup assembly 3. During testing, fiber 4 is unwound from a payout spool 5 of the payoff assembly 1, pulled over multiple capstans 8, 9 and 10 in the proof test assembly 2 and then taken up on a takeup spool (not shown) of the takeup assembly 3. The capstans 8, 9 and 10 of the proof test assembly 2 exert a predetermined amount of stress on the fiber 4. If the fiber 4 breaks as a result of the stress exerted on it, the fiber 4 on the payout spool 5 is deemed to be unfit for installation, and therefore is not distributed to customers.

[0003] Proof testing subjects the entire length of fiber to tensile stress for a predetermined period of time. Under such tests, fiber with unacceptably large flaws will break. Currently, the industry standard for the level of stress that a fiber must be capable of withstanding is 50,000 pounds per square inch (50 kpsi). If a fiber can withstand this amount of stress, it is deemed to be suitable for installation. In other words, the fiber is believed to be capable of surviving the stress levels that will likely be exerted on it during installation. Of course, proof testing at higher stress levels can be performed if desired.

[0004] Referring again to FIG. 1, a head stock 6 and tail stock 7 maintain the spool 5 in a suspended position above the floor. The head stock 6 comprises a motor (not shown) that turns the shaft 11 of the spool 5 and the tail stock comprises a bearing (not shown) that allows the shaft 11 of the spool 5 to turn. The tail stock 7 comprises a motor (not shown) that turns the screw 13. As the fiber 4 is unwound from the spool 5, the position of the fiber changes laterally (in the axial direction of the shaft 11). The fiber 4 goes under a first sheave 18 and then over a second sheave 19. The first and second sheaves 18 and 19 are mounted on a follower 14, which moves along the screw 13 as the screw 13 is turned. The second sheave 19 is stationary and is attached to the follower 14 by attachment member 22. The first sheave 18 is not fixedly secured, but is turned by the fiber 4 coming off of the spool 5 as the position from which the fiber 4 is coming off of the spool 5 changes.

[0005] The fiber 4 goes from the sheave 19 under another sheave 22 and over a dancer 23. The dancer 23 moves as the tension on the fiber 4 changes. The fiber passes over the dancer 23, over pull capstan 8, under prooftest sheave 9, over prooftest capstan 10, over dancer 24, under sheave 25 and into the takeup assembly 3. These components of the prooftest assembly 2 are controlled to cause a predetermined amount of stress to be placed on the fiber 4. The prooftest assembly 2 comprises rewinder control circuitry 15 that controls all of the components of the rewinder machine.

[0006] As the sheave 18 of the payout assembly 1 turns, the angle of the sheave 18 is detected by circuitry (not shown) inside of the follower 14. The sheave 18 is mounted on a bearing assembly 21 that rotates in side of a rotary variable inductive transformer (RVIT) (not shown) in the follower 14 as the sheave 18 turns. The sheave 18, the bearing assembly 21, the sheave 19, the sheave attachment member 22 and the follower 14 can be thought as the follower assembly. The current passing through the transformer changes as the bearing rotates, and this current is used to determine the angle between the sheave 18 and the position that the fiber 4 is coming off of the spool 5. This angle is typically referred to as the fleeting angle. Generally, sensor signals 16 are output from the follower 14 and received by the rewinder control circuitry 15 of the prooftest assembly 2. The rewinder control circuitry 15 processes the sensor signals 16 and determines the fleeting angle. Because the fleeting angle must be prevented from becoming too large, the rewinder control circuitry 15 generates control signals 17 that are sent to the motor in the tail stock 7 that turns the screw to cause it to turn the screw 13. As the screw 13 turns, the follower 14 moves in the transverse direction toward the transverse position of the fiber 4 on the spool 5, thereby reducing the fleeting angle.

[0007] Providing the sheave 18 with the ability to turn in this manner presents some problems. The combination of the sheave 18 and bearing assembly 21 must be very light because it must be capable of being turned by the moment around the bearing produced by the fiber 4 under very low tension. The low inertia and friction caused by the tension will often set up oscillations in the sheave 18, which result in oscillations in the fleeting angle. These oscillations can result in variations in the control signals 17 and can cause the fiber 4 to jump off of the sheave 18. The variations in the control signals 17 can result in improper movement of the follower 14. In addition, manufacturing differences in the sheaves 18 and 19 make each one slightly different, which can result in variations in mechanical performance of the sheaves 18 and 19. Also, the distance between the sheave 18 and the fiber 4 coming off of the spool changes, which results in changes in the length of the fiber 4 relative to the dancers 23 and 24. These changes in length can produce large motions in the dancers 23 and 24, which can destabilize the rewinder machine.

[0008] A need exists for a rewinder method and apparatus that eliminate oscillations in the follower sheave, prevent variations in the control signals that control the movement of the follower assembly, and prevent destabilization of the rewinder machine.

SUMMARY OF THE INVENTION

[0009] The present invention provides a rewinder method and apparatus. The payout assembly of a rewinder machine comprises a spool having optical fiber wrapped about it, a motor that turns the spool as fiber is unwound from the spool, a first sheave having a surface along which the unwound fiber passes, a load cell in direct contact with the first sheave, and a motion mechanism for producing relative motion between the spool and the first sheave. The load cell senses stress exerted on the first sheave by the fiber as the fiber passes along a surface of the. The load cell produces electrical signals relating to the fleeting angle between the first sheave and the position on the spool from which fiber is being unwound. A controller receives the electrical signals and generates control signals that cause the motion mechanism to produce relative motion between the spool and the first sheave in a direction substantially parallel to an axis of rotation of the spool to reduce the fleeting angle.

[0010] In accordance with the preferred embodiment, the motion mechanism is mounted on a follower component and comprises a screw and a motor. The follower component is movably mounted on the screw. The motor receives the control signals from the controller and rotates the screw in accordance with the control signals to cause the follower component to move in a direction substantially parallel to an axis of rotation of the spool such that the fleeting angle is reduced.

[0011] Preferably, the load cell is embedded in the first sheave and the first sheave is fixedly secured to the follower component. Fixedly securing the first sheave to the follower component prevents the sheave from oscillating and therefore prevents all of the aforementioned problems that can result from oscillation of the sheave. Furthermore, because the load cell is used, the need for a rotary variable inductive transformer (RVIT) is obviated. In addition, the load cell is capable of very accurately sensing the fleeting angle. Therefore, the control signals produced by the controller are very accurate, which ensures that the movement of the follower component is correct and will result in a reduction of the fleeting angle.

[0012] The present invention also provides a method for use in a rewinder machine for sensing a fleeting angle and for reducing the fleeting angle. The fleeting angle corresponds to an angle between a position on the spool from which optical fiber is being unwound and the location of the first sheave along which unwound optical fiber passes. The method comprises the steps of: sensing the fleeting angle with a load cell that is in direct contact with the first sheave, sensing the stress exerted on the first sheave with the load cell. The load cell produces electrical signals relating to the angle between the position on a spool from which optical fiber is being unwound and the location of the first sheave.

[0013] The method also includes the step of processing the electrical signals to determine the amount of relative motion needed between the first sheave and the spool to reduce the fleeting angle. Control signals are generated based on the determination as to the amount of relative motion needed between the first sheave and the spool to reduce the fleeting angle.

[0014] These and other features and advantages of the present invention will become apparent from the following description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a front view of a known rewinder machine.

[0016]FIG. 2 is a front view of the rewinder machine of the present invention in accordance with one embodiment.

[0017]FIG. 3 is a front view of the rewinder machine of the present invention in accordance with another embodiment.

[0018]FIG. 4 illustrates a flow chart of the method of the present invention in accordance with one embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] In accordance with the present invention, the first sheave of the follower assembly is fixedly secured to the follower. This can be seen in FIG. 2. FIG. 2 is a front view of the rewinder machine 30 of the present invention in accordance with an example embodiment. Except for the follower assembly of the present invention discussed below, the rewinder machine 30 of the present invention may be similar or identical to the known rewinder machine shown in FIG. 1. For example, the head stock 6, tail stock 7, spool 5 and screw 13 shown in FIG. 1 are also suitable for use with the present invention. The present invention will be described with reference to a rewinder machine having a configuration similar to the rewinder machine shown in FIG. 1. However, the present invention is not limited to any particular rewinder machine configuration.

[0020] With reference again to FIG. 2, in accordance with the present invention, the first sheave 48 is fixedly secured to the follower 33 by attachment member 51. The second sheave 49 is fixedly secured to the follower 44 by attachment member 52. These components, namely, the attachment members 51 and 52, the sheaves 48 and 59, and the follower 44 constitute the follower assembly. The rewinder machine 30 has a payout assembly 31 that comprises a head stock 36 and a tail stock 37, which maintain the spool 35 in a suspended position above the floor. The head stock 36 comprises a motor (not shown) that turns the shaft 41 of the spool 35. The tail stock 37 comprises a bearing mechanism (not shown) that allows the shaft 41 to rotate, thereby rotating the spool 35.

[0021] The tail stock 37 comprises a motor 38 that turns the screw 43 in accordance with control signals 57 received from rewinder control circuitry 58. As the fiber 34 is unwound from the spool 35, the position of the fiber 34 changes laterally (i.e., in the axial direction of the shaft 41). The fiber 34 goes under a first sheave 48 and then over a second sheave 49. The first and second sheaves 48 and 49 are mounted on a follower 14, which moves along the screw 13 as it turns. The first and second sheaves 48 and 49 are stationary and are attached to the follower 44 by attachment members 51 and 52, respectively.

[0022] The fiber 34 passes under the sheave 49, under another sheave 62 and over dancer 63. The dancer 63 moves as the tension on the fiber 34 changes. The fiber passes over the dancer 63, over pull capstan 68, under prooftest sheave 69, over prooftest capstan 70, over dancer 71, under sheave 72 and into the takeup assembly 3. These components of the prooftest assembly 2 are controlled by the rewinder control circuitry 65 to cause a predetermined amount of stress to be placed on the fiber 34. The prooftest assembly 32 comprises rewinder control circuitry 65 that controls all of the components of the rewinder machine 30.

[0023] As stated above, the rewinder machine of the present invention is not limited to any particular configuration. The rewinder machine of the present invention has been described with reference to one particular embodiment for the purposes of providing an example of one possible configuration of the rewinder machine. Rewinder machines having many different configurations exist and are known to those skilled in the art. Those skilled in the art will understand from the present disclosure that present invention covers rewinder machines of all different types and configurations.

[0024] In accordance with the present invention, the RVIT assembly of the follower and RVIT assembly 14 shown in FIG. 1 is not necessary. Because the sheave 48 is fixedly secured to the follower 44, the complications associated with enabling the sheave 48 to rotate and the problems caused by oscillations in the sheave 48 are eliminated. In accordance with the preferred embodiment of the present invention, a small, very sensitive load cell 40 is embedded in or secured to the sheave 48. As the position from which the fiber 34 is coming off of the spool 35 changes, stress is placed on the sheave 48 by the fiber 34. The load cell 40 senses this stress and produces an electrical signal, which is output to rewinder control circuitry 65. The rewinder control circuitry 65 receives the electrical signal and generates control signals 57 based on the received electrical signals. The control signals 57 are delivered to the motor 38 that drives the screw 43. The motor 37 turns the screw 38 in accordance with the received control signals until the follower 44 is aligned with the fiber 34 coming off of the spool 35.

[0025] The load cell 40 that is used for this purpose is not limited to any particular type or material. The load cell 40 should be small enough not to detrimentally affect the function being performed by the sheave 48 and not to place more stress on the fiber 34. The load cell 40 should be sufficiently sensitive to detect small levels of stress in the sheave 48. It will be understood by those skilled in the art that a variety of transducers are available that have these characteristics.

[0026] It should be noted that while FIG. 2 demonstrates the manner in which the present invention works when the follower 44 is moved along the screw 43, the present invention applies equally to rewinder machines that move the spool while keeping the sheaves 48 and 49 stationary. In the latter case, the load cell 40 still senses the fleeting angle and outputs corresponding electrical signals 56 to the rewinder control circuitry 65. However, the control signals 57 produced by the rewinder control circuitry 65 are delivered to a motion mechanism that moves the spool in a direction and by an amount dictated by the control signals 57 to reduce or eliminate the fleeting angle.

[0027]FIG. 3 illustrates a front view of a rewinder machine 80 in accordance with another embodiment of the present invention, wherein the spool is moved along its axis of rotation rather than moving the first sheave. Only the components that are different from the components shown in FIG. 2 have been renumbered. The components in FIG. 3 that are labeled with the same numbers that the components in FIG. 2 are labeled with perform the same functions as those described above with reference to FIG. 2. Therefore, those components will not be discussed with reference to FIG. 3 in the interest of brevity.

[0028] In accordance with this embodiment, the payoff assembly 81 comprises a motion mechanism 82 that imparts motion to the spool 35 in accordance with the control signals 57 received from the rewinder control circuitry 65 to reduce the fleeting angle. The first and second sheaves 48 and 49 are attached to a stationary sheave platform 83 by their respective attachment members 51 and 52. As in the embodiment represented by FIG. 2, the load cell 40 senses stress on the first sheave 48 created by the tension on the fiber 34 at the fleeting angle and produces electrical signals 56 relating to the fleeting angle. The rewinder control circuitry 65 processes the electrical signals 56 and produces control signals 57 that are delivered to the motion mechanism 82. The motion mechanism then causes the spool 35 to move in accordance with the control signals in a direction that reduces the fleeting angle.

[0029]FIG. 4 illustrates a flow chart of the method of the present invention in accordance with the preferred embodiment. In accordance with the method, the fleeting angle is sensed by the load cell in contact with the first sheave, as indicated by block 81. The load cell produces electrical signals relating to the angle between the position on the spool from which optical fiber is being unwound and the location of the first sheave, as indicated by block 82. The electrical signals are then processed by the rewinder control circuitry 65 to determine the amount of relative motion needed between the spool and the first sheave to reduce the fleeting angle. This step is represented by block 83. The controller then generates controls signals that are based on the amount of relative motion needed to reduce the fleeting angle, as indicated by block 84. The control signals are then fedback to the payout assembly 31 to cause the appropriate motion to be imparted to reduce the fleeting angle.

[0030] From all of the above, it can be seen that by placing the load cell in direct contact with the first sheave and by fixedly attaching the first sheave to the follower 44 (FIG. 2) or to the sheave platform 72 (FIG. 3), oscillations in the first sheave are prevented. Furthermore, by preventing these oscillations, the signals produced by the load cell 40 more accurately represent the fleeting angle, which improves the integrity of the control signals fedback to control the motion of the follower 44 (FIG. 2) or spool 35 (FIG. 3). The overall result is a more robust rewinder machine that produces more accurately proof tests fiber.

[0031] It should be noted that the present invention has been described with reference to the preferred embodiments and that it is not limited to these embodiments. Modifications, additions and/or deletions can be made to the embodiments described herein without deviating from the scope of the present invention. Those skilled in the art will understand in view of the discussion provided herein that all such modifications, deletions and additions are within the scope of the present invention. 

What is claimed is:
 1. A rewinder machine comprising: a payout assembly, the payout assembly comprising: a spool having optical fiber wrapped thereabout; a motor that turns the spool as fiber is unwound from the spool; a first sheave having a surface along which the unwound fiber passes; a load cell in direct contact with the first sheave, the load cell sensing stress exerted on the first sheave by the fiber as the fiber passes along a surface of the first sheave, the load cell producing an electrical signal relating to an angle between the first sheave and a position on the spool from which fiber is being unwound; a motion mechanism, the motion mechanism producing relative motion between the spool and the first sheave in accordance with control signals received by the motion mechanism; and a controller, the controller receiving the electrical signals produced by the load cell and generating the control signals based on the received electrical signals, the controller outputting the electrical signals to the motion mechanism to cause the motion mechanism produce relative motion between the spool and the first sheave in a direction substantially parallel to an axis of rotation of the spool and such that the angle is reduced; a prooftest assembly, the proof test assembly receiving unwound fiber from the payout assembly and exerting a predetermined amount of stress on the fiber; and a takeup assembly, the takeup assembly receiving fiber from the prooftest assembly that has been prooftested and taking the fiber up on a takeup spool.
 2. The rewinder machine of claim 1, wherein the load cell is embedded in the first sheave.
 3. The rewinder machine of claim 1, wherein the motion mechanism is mounted on a follower component and comprises a screw and a motor, the follower component being movably mounted on the screw, the motor receiving the control signals from the controller and rotating the screw to cause the follower component to be moved in said direction substantially parallel to an axis of rotation of the spool such that said angle is reduced.
 4. The rewinder machine of claim 3, wherein the first sheave is rotationally attached to an attachment component, and wherein the attachment component is fixedly secured to the follower component.
 5. The rewinder machine of claim 1, wherein the motion mechanism receives the control signals from the controller and causes the spool to be moved in said direction substantially parallel to an axis of rotation of the spool such that said angle is reduced.
 6. The rewinder machine of claim 1, further comprising: a second sheave, the second sheave being fixedly attached to the follower component by an attachment member, wherein the fiber that is unwound from the spool passes underneath the first sheave and then over the second sheave, and wherein as the fiber passes underneath the first sheave, the load cell senses stress in the first sheave and converts the sensed stress into said electrical signal.
 7. A follower assembly for use in a payout assembly of a rewinder machine, the follower assembly comprising: a follower component movably mounted on a screw such that when the screw is turned, the follower assembly moves along the screw; a first sheave fixedly attached to the follower component by an attachment component, the first sheave being rotationally mounted to the attachment component, wherein fiber unwound from a spool rotationally mounted in the payoff assembly passes along a surface of the first sheave; and a load cell in direct contact with the first sheave, the load cell sensing stress exerted on the first sheave by the fiber as the fiber passes along the surface of the first sheave, the load cell producing an electrical signal relating to an angle between the first sheave and a position on the spool from which fiber is being unwound.
 8. The follower assembly of claim 7, wherein the load cell is embedded in the first sheave.
 9. The follower assembly of claim 7, further comprising: a second sheave, the second sheave being fixedly attached to the follower component by an attachment member, wherein, the fiber that is unwound from the spool passes underneath the first sheave and then over the second sheave, and wherein as the fiber passes underneath the first sheave, the load cell senses stress in the first sheave and converts the sensed stress into said electrical signal.
 10. A method for use in a rewinder machine for sensing a fleeting angle and for reducing the fleeting angle, the fleeting angle corresponding to an angle between a position on a spool from which optical fiber is being unwound and the location of a first sheave along which unwound optical fiber passes, the method comprising: sensing the fleeting angle with a load cell that is in direct contact with the first sheave, wherein the passage of unwound fiber along the first sheave causes stress to be exerted on the first sheave; producing electrical signals with the load cell relating to the angle between the position on a spool from which optical fiber is being unwound and the location of the first sheave; and processing the electrical signals to determine the amount of relative motion needed between the first sheave and the spool to reduce the fleeting angle; and generating control signals based on the determination as to the amount of relative motion needed between the first sheave and the spool to reduce the fleeting angle.
 11. The method of claim 10, further comprising: delivering the control signals to a motion mechanism, the motion mechanism producing relative motion between the spool and the first sheave in accordance with control signals received by the motion mechanism, and wherein the relative motion produced by the motion mechanism causes the fleeting angle to be reduced.
 12. The method of claim 10, wherein the motion mechanism is mounted on a follower component and comprises a screw and a motor, the follower component being movably mounted on the screw, the motor receiving the control signals from the controller and rotating the screw to cause the follower component to be moved in a direction substantially parallel to an axis of rotation of the spool to reduce the fleeting angle.
 13. The method of claim 10, wherein the first sheave is rotationally mounted on an attachment member, and wherein the attachment member is fixedly attached to the follower component.
 14. The method of claim 10, wherein the motion mechanism receives the control signals from the controller and causes the spool to be moved in a direction substantially parallel to an axis of rotation of the spool to reduce the fleeting angle. 